OK, for the trifecta....
I've compiled some 16x12 0x0 and 4x16 #s from sites MikeC didn't include but that I thought merited equal attention. I'm also going to split the #s a bunch of different ways b/c I'm stupid (massochistic) like that. I'll accept the fact that we're comparing two cards that I don't consider reasonable purchases for various reasons, just b/c I don't want to redo MikeC's work. (So I'm not a total massochist--sue me.

)
MikeC's chart takes #s from AT, ET, FS, HH, TR, and Xbit, and gives the X1900XTX a win-loss-draw total of 43-38-2.
My chart takes #s from ComputerBase.de, Digit-Life.com (aka iXBT), Hardware.fr (aka BeHardware.com), Hexus.net, Rage3D, and ZDNet.de. Yeah, a few foreign sites, but they've been around a while and seem solid. These sites give the XTX a record of 49-44-3, so still pretty close.
Combining both, the XTX is 92-82-5. Here's a summary.
I'm going to wander off the beaten path, so feel free to skip this italicized bit.
It might be more enlightening to work with the #s a bit. For instance, I've always thought calling 33 vs. 32fps a win was a bit of a stretch. So I got a bit more liberal with the conditions for a draw. Let's see how the
If I define a draw as:
<5% difference, XTX is 79-62-38.
<10% difference, XTX is 60-50-69.
<15% difference, XTX is 50-45-84.
The XTX still wins more tests than the GTX-512, and its win percentage declines only slightly. So, no real change. I think pushing a "draw" up to even 15% is fair, as I'm not sure you'll easily notice 30 vs. 34.5fps, or even 100 vs 115fps. But that's just me.
But do we really consider 16x12 without AA a valid test for these $650+ cards? Let's focus on two more enthusiast-oriented settings, HDR and AA+AF.
HDR is tricky, as there are only five games with explicit HDR modes, some of them don't run with the same precision on each card (which can result in visible differences), and some of these "HDR" modes don't appear to be anything more than a bloom effect (which blinds you, more than anything).
In the five "HDR" games--AoE3, FC, HL2:LC, SC:CT, and SS2--the XTX's record at 16x12 0x0 is 6-2-0. Again, not really an even comparison, but it's there.
AA+AF is a bit easier to compare, as both cards should default to similar IQ benefits (ignoring HQ AF and TAA/AAA). So, looking
at 16x12 w/ 4xAA & 8/16xAF #s, the XTX is 28-22-1.
Again, NV is still the convincing OpenGL champ. Tho ATI closed the gap in Doom 3 and Quake 4, NV still rocks in IL-2, Pacific Fighters, and Riddick.
I'm still not convinced XTX vs. GTX-512 is a worthwhile comparison, though, as the XTX is overpriced compared to the XT and the GTX-512 as a single-card solution is both hard to find and overpriced relative to its performance vs. the XT(X). If we look down a notch, it's also not quite fair to compare a X1900XT to a 7800GTX b/c of different street prices ($490 vs. $445) and RAM sizes (512 vs 256MB)--but the X1900XT wins just about every benchmark in this comparison, so it's easier to justify its price. Comparing a X1900XTX to a 7800 GTX-512 seems more an academic exercise than anything else, but at least the GTX-512 is a better hint of what's to come with the 7900. Obviously it's not a great hint, especially if the 7900 will sport significant increases in
both core clock and # of pipes, but it's better than jumping from a GTX-256.
Aaaanyway, a few more weeks til 7900. Can't wait to see if NV's gonna do some "housecleaning" with ATI.
